The primary objective of the proposed research is to elucidate the genetic organization of adenovirus type 2 DNA and its relation to the expression of specific viral genes during infection and oncogenic transformaton of mammalian cells. The approach emphasizes the application and development of methods for physical localization, on a map of the viral genome, of regions which correspond to defined classes of virus-coded mRNA isolated from infected or transformed cells. The specific methods for such physical mapping include hybridization of viral mRNA with complementary strands of radioactive viral DNA. More specific probe DNA will be prepared by cleavage of viral DNA with bacterial restriction enzymes, limited digestion of selected cleavage fragments of viral DNA with exonuclease III, and specific 3' terminus labeling using an RNA-dependent DNA polymerase. Application of electron microscopy for hybridization-mapping is also proposed. The overall goal of the proposal mapping experiments is to localize regions of the viral genome expressed in transformed cells and relate this (these) region(s) to the temporally selective genome expression of Ad 2 ir infected cells. A new approach to the identification and quantitation of integrated viral DNA in transformed cells is presented, based on the available complement-specific viral DNA probes used throughout the RNA:DNA hybridization mapping study.